<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        .divc {
            background-color: red;
        }
    </style>
</head>
<body>
    <div id="app">
        <button @click="inc">fontSize</button>
        <div :style="{color: color,backGroundColor: backGroundColor,fontSize:fontSize}">
            {{message}}
        </div>
    </div>
</body>
</html>
<script src="https://unpkg.com/vue@3/dist/vue.global.js"></script>
<script>
    const { createApp } = Vue;
    createApp({
        data() {
            return {
                fontSize:30,
                color:'red',
                backGroundColor:'green',
                message: 'Hello Vue!'
            }
        },
        methods: {
            inc(){
                this.fontSize+=20;
            }
        },
    }).mount('#app');
    
</script>